Great Ancoats Street

During February 2009, two compounds were established for construction of the Great Ancoats Street (Inner Relief Road) underpass. One fenced off the eastern end of Longacre and Chapeltown Streets. It extended from the eastern side of Fair Street to the western side of Great Ancoats Street, except for the north side pavement of Chapeltown Street. The second larger compound enclosed most of the cleared land between Pollard Street and the Ashton Canal, from Great Ancoats Street to Munday Street. In addition to the underpass ramp, it housed site offices and materials for the expansion, such as new track. The scale of the work is further reflected in the workforce required — the temporary offices on site could accommodate up to 300 people.

Work on the underpass and new line in the Great Ancoats Street area started in April 2009. The first phase of piling work — creating tram underpass retaining walls, on both sides of Great Ancoats Street — finished in June 2009 ahead of schedule. Parts of the top of the underpass, on both sides of Great Ancoats Street, were completed and utility diversion work took place during the second half of 2009.

In 2010 piling first for the western then the eastern halves of Great Ancoats Street took place. During the work, road traffic had one lane in each direction on the other half of Great Ancoats Street. The underpass was then excavated, and the walls have been brick lined.

Construction

The underpass was constructed using the ‘cut and cover’ method. Before excavation could take place, retaining walls were formed using using the Continuous Flight Auger (CFA) technique. There are more than 400 concrete piles ranging in diameter from 0.9 to 1.5 metres set 15 metres deep. They support the excavation and are load–bearing for the underpass roof which will carry both road and pavements. CFA piling causes minimum disturbance it is ideal for noise and environmentally–sensitive sites like this city centre project.

A hollow–stemmed continuous flight auger is rotated into the ground to the required depth. As the auger is withdrawn, plasticised concrete is pumped down the hollow stem under balancing pressure, forming a shaft of liquid concrete to ground level, maintaining support to the sides of the shaft. A reinforcing cage is then inserted by hand or vibrator for deeper piles. The cage is provided with welded spacers, which centralise it within in the pile bore, and the cage is secured at the required top level.

Over the course of the work on the underpass MPact–Thales — the consortium appointed to design, build and maintain the new lines — moved up to 20,000 cubic metres, the equivalent of 20 million litres, of soil.

A groundbreaking day for Metrolink, 6 April 2009.

The photograph above shows Councillor Matt Colledge, Chair of GMITA, with Bryan Diggins, Project Director, MPact–Thales, and Philip Purdy, GMPTE's Metrolink Director, looking down a reinforcing cage, which are being used as part of the piling work.

The photograph to the left shows Mr Purdy, Councillor Colledge and Mr Diggins in front of the piling rig.